Not quite, according to the city's police; the lamb is actually more likely to be rat, fox or mink.

On May, 63 suspects were arrested for a racket that makes horse meat in hamburgers seem positively palatable.

For the past four years, the police said, the gang had taken the small mammals, doused their flesh in dye and preservatives, and sold it as lamb "at farmers' markets in Jiangsu and Shanghai".

In a raid, nearly 10 tons of the counterfeit lamb was confiscated from a warehouse and the police said the gang had made profits of at least £1 million.

"How many rats does it take to put together a sheep?" asked one user of Weibo, China's version of Twitter.

There was weary resignation, rather than surprise, at the latest revelations in a city that is already accustomed to its food being cooked in oil dredged from the sewers, and where more than 16,000 putrefying pig carcasses were found dumped in a river that provides drinking water earlier this year.

However, the Shanghai police took the time to give advice on the internet on how to spot fake lamb.

"In fake lamb, it is easy to pull apart the fat from the red meat. In real lamb, the fat is difficult to separate," the police said on Sina Weibo, in a post that was forwarded more than 10,000 times.

The arrests in Shanghai were part of a countrywide operation since the beginning of the year to reassure the public that their food is safe.

A total of 904 people were arrested for selling fake, poisonous or contaminated meat and more than 1,700 underground butchers and processors were closed down.